The present invention claims priority from Canadian Application No. 2,324,215, filed Nov. 6, 2000, which application is incorporated herein by reference.
The present invention relates to the biocontrol of weed growth using a bioherbicide. More specifically, the present application pertains to the use of a fungal bioherbicide for the control of cleavers.
Cleavers [false cleavers (Galium spurium L.) and cleavers (G. aparine L.)] are weeds of important economic impact in western Canada, especially for producers of canola (Brassica napus L. and B. rapa L.) (Malik and Vanden Born, 1988). Weed surveys in the prairie provinces of Canada have indicated that cleavers populations have increased during the past 10 years and their abundance ranking have increased more rapidly than other cropland weeds (Thomas, 1998). Heavy infestations of cleavers in canola cause severe yield losses, up to 18% with 100 false cleavers plants/m2 through crop/weed competition (Malik and Vanden Born, 1987). Another problem with cleavers in canola is that cleavers seeds are similar in shape and size to canola seeds, making mechanical seed separation difficult. Cleavers seed contamination in canola leads to downgrading of canola quality, has implications for the crushing industry, and contributes to the spread of weed infestations. Under legislation in the Canada Seeds Act, no cleavers seed is allowed in pedigreed canola seed and thus pedigreed seed producers of canola cannot tolerate land infested with these weeds. Cleavers are not only difficult to control in canola but are an increasing problem in other major crops of Western Canada such as spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and pea (Pisum sativum L.).
Considerable efforts have been made to find effective herbicide controls for cleavers over the past decade. Chemical herbicides used for cleavers control include several acetolactate synthase (ALS) inhibitors along with auxin-type herbicide combinations. Unfortunately, herbicide resistance has been detected in populations of false cleavers (Hall et al., 1998). This herbicide-resistant false cleavers biotype shows cross-resistance to quinclorac and ALS inhibitors, including imazethapyr, one of the products for which herbicide-tolerant canola has been developed. With continuing herbicide use and herbicide-tolerant canola cultivation (approximately 20-40% or more of the canola acreage in Canada), herbicide resistance may become more common in false cleavers.
To date, no bioherbicides are available for control of cleavers. Thus, there is a need in the art for new or alternative cleavers control strategies. There is also a need in the art for cleaver control strategies for both conventional and herbicide tolerant (HT) canola. Further there is a need for biological control agents that complement herbicide use by introducing novel modes of action to mitigate herbicide resistance development and to provide a component within an integrated pest management system.
It is an object of the invention to overcome disadvantages of the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.
The present invention relates to the biocontrol of weed growth using a fungal bioherbicide.
According to the present invention there is provided a biocontrol agent comprising Plectosporium tabacinum CL98-103. Preferably, the biocontrol agent comprises Plectosporium tabacinum CL98-103 deposit number PTA-3463 (ATCC).
Also according to the present invention, there is provided a composition comprising the biocontrol agent (P. tabacinum CL98-103) and a carrier. Any carrier that permits the biocontrol agent to be delivered to a target plant in a manner such that the biocontrol agent remains viable and pathogenic may be employed in the composition. Examples of carriers include, but are not limited to clay, alginate, diatomaceous earth, growth medium, or a combination thereof. The growth medium may comprise solid growth medium or liquid growth medium or a combination thereof. Solid growth medium may comprise potato dextrose agar, Czapek-Dox agar, lima bean agar, V-8 juice agar, oatmeal agar, tryptic soy agar, dextrose tryptone agar, Cooke rose bengal agar, prune agar, malt extract agar, synthetic nutrient poor agar, Sabouraud dextrose agar, water agar, cornmeal agar or a combination thereof. Liquid growth media may comprise V-8 juice medium, Modified Richard""s solution (MRS), Yeast extract broth (YEB), Richard""s solution (RS), Czapek-Dox broth (CDB), Trichoderma medium (TM), Tryptic soy broth (TSB), Potato dextrose broth (PDB), Nutrient broth (NB), Colletotrichum truncatum medium (CTM), Malt extract broth (MEB) or a combination thereof.
Also according to the present invention, there is provided a method for controlling weeds, herbicide-resistant and herbicide-susceptible cleavers, herbicide-resistant and herbicide-susceptible false cleavers, and other weeds by infecting them with the biocontrol agent defined above. The biocontrol agent may be administered to the cleavers in combination with a herbicide. Preferably, the biocontrol agent is administered to the weeds at about the one whorl stage or earlier.
Further according to the present invention as defined above, the biocontrol agent or composition comprising the biocontrol agent may additionally comprise a surfactant. Preferably the surfactant is Silwet L-77, and is present in an amount of about 0.05% to about 0.1% by volume.
Also according to the present invention as defined above, there is provided a composition comprising spores of Plectosporium tabacinum CL98-103 and a carrier.
Further, according to the present invention there is provided a method for the biocontrol of a weed plant under non-aquatic conditions, or conditions that do not requiring periodic submersion, using Plectosporium tabacinum as a biocontrol agent.
Also according to the present invention, there is provided a method for growing and producing spores of Plectosporium tabacinum CL98-103, comprising growing the fungal biocontrol agent or spores thereof in a suitable liquid medium.
This summary of the invention does not necessarily describe all necessary features of the invention but that the invention may also reside in a sub-combination of the described features.